Intermittent fasting is one of the top weight loss trends around. Read on to learn the pros and cons of this popular approach to eating.
One of the hottest diets trending around the world today, intermittent fasting has soared in status as evidence continues to mount of its ability to help millions lose weight and potentially even help us live longer.
But this approach to eating does carry some real risks that you should know about before diving into a fasting lifestyle.
What is intermittent fasting?
As its name suggests, intermittent fasting is an eating pattern that cycles between scheduled eating periods and fasting periods. There are lots of ways to fast intermittently, but the most popular are the time restricted feeding, alternate day fasting, and 5:2 methods.
Time restricted feeding limits the hours you can eat to a specific time window, say between 10:00 am and 6:00 pm.
Alternate day fasting involves eating no food, or only 25% of your daily calories, every other day, and eating with no restrictions on non-fast days.
The 5:2 approach involves eating normally for five days followed by a two-day reduction in calories to only 500 for women and 600 for men.
Flipping the metabolic switch: the important role ketones play
After we eat, glucose is released into the blood and used for energy to fuel the body, while fat is stored in our tissues as triglycerides.
Around 12 hours after a last meal, our body senses that glucose is in short supply, so it triggers the triglycerides, or fat, to break down into fatty acids.
These fatty acids are then converted by the liver into units called ketones. Ketones then circulate back into the bloodstream and are used to provide fuel for the body and brain.
In other words, when our body detects that food is not available, the metabolism shifts from storing fat to mobilizing and burning fat to supply the muscles and brain with energy.
Tatiana Keay, weight loss dietitian at Digestive Disease Consultants of OC, adds that “While you may lose weight on a calorie restricted diet, the human body is programmed to return to the previous metabolic set-point. Intermittent fasting has a different effect on the body by directly targeting your set-point.”
What are the perks of intermittent fasting?
Apart from being an alternative source of fuel, ketones seem to trigger a number of cellular responses that positively influence health and aging in other important ways:
Promotes weight loss. Mounting evidence shows that intermittent fasting can help you shed pounds. One study found that fasting on alternate days between just 3 and 12 weeks can result in reducing body weight by 3% to 7% and body fat by 6.6 lbs to 12lbs.
Increases insulin sensitivity. Time restricted feeding can dramatically lower insulin levels and improve insulin sensitivity. A 2018 study showed that men with prediabetes who ate within a 6-hour daily window over five weeks decreased their fasting insulin by 3.4 mU/L and insulin resistance by 36 U/mg.
Boosts heart health. Following a 5:2 eating pattern for 12 to 24 weeks can lower total cholesterol by 5% to 20% and triglycerides by 17% to 50%, and five weeks of time restricted eating can reduce systolic and diastolic blood pressure by 11 mmHg and 10 mmHg respectively.
Improves cognitive health. Many report a heightened state of mental alertness and better executive function, working memory, and verbal memory during fasting periods.
The downsides of intermittent fasting
Fans of intermittent fasting boast its long list of potential benefits, but keep in mind that most of its test subjects to date have been animals.
Human studies do exist, but more research will need to be done before this way of eating can be fully recommended. Also, strict fasting is pretty hard to stick to, and the intense hunger and inability to concentrate on fast days are hurdles often too tough to overcome.
People with chronic conditions like diabetes, heart disease, cancer, and COPD are at higher risk of side effects like dizziness, nausea, migraine headaches, and general weakness.
If you are considering intermittent fasting, it is best to consult with your healthcare provider to make sure this eating approach is safe for you.
Also, if you are struggling with an eating disorder or are prone to one, avoid intermittent fasting as there is a major association between this pattern of eating and bulimia nervosa.
The bottom line
Intermittent fasting is a weight loss tool that shows promise, but may not be recommended for everyone. If you decide to try intermittent fasting, keep in mind that the quality of the food you do eat is crucial. As with any approach to eating, your food must be well-balanced so that you get the right nutrition to maintain energy throughout the day. You should never eat in a way that will put your health at risk due to nutritional deficiencies.
Note: There are many diet programs available, each with its pluses and minuses. When choosing a diet for yourself, it is best to research the difference between diets to find one that best meets your individual needs.